Making seamless tubing by continuous process

ABSTRACT

Method of and apparatus for casting seamless tubing wherein the apparatus includes a revolving mold and an open bottom, pressurized stationary bell positioned within said mold and spaced therefrom to form an annulus for the tubing to be cast. The mold is water cooled and a gaseous cooling medium is supplied to the open area under the bell for both cooling the interior wall of the tubing and pressurizing such wall to prevent collapse of the tubing.

[ Oct. 29, 1974 United States Patent Bucci FOREIGN PATENTS OR APPLICATIONS 7/1961 Germany Germany 6647 0276 1 0589 7336 2 80 5 I 2 d R r 3 Y m G m m m B H S ws a S W 7 u 9 E B L M 9 M "a s Awwm m w o RA N U Gm u N 0 T t. K m 0 A0 V M MCm F M m H U U U [21] Appl. No.1 196,063 Primary ExaminerR. Spencer Annear Attorney, Agent, or FirmWilliam B. Jaspert; Donald D. Jeffrey ABSTRACT Method of and apparatus for casting seamless tubing wherein the apparatus includes a revolving mold and an open bottom, pressurized stationary bell positioned within said mold and spaced therefrom to form an annulus for the tubing to be cast. The mold is water cooled and a gaseous cooling medium is supplied to the open area under the bell for both cooling the interior wall of the tubing and pressurizing such wall to prevent collapse of the tubing.

8 Claims, 7 Drawing Figures 22 a 45 001 88XXX 8 8 446 /l i 886 4 2 66/// M MMM I i 2 i 111 3 mmm 42 0 S 6 7 T 14 3 N 4 4 6% W 6 .lP 0 l m S mn mm "m E u WT .me "o N n m ddh d n RT m wmw m .mSCLBBL n e m mm Rm fifiwmfl m m& I99999 L NHHHHH d .I 5 M 35469 U IF 57875 4 075 2 HM m 42380 5 55 5 rll. 3333 PATENTEB-m 291934 slm am 3 INVENTOR. H7552? 5066/ BACKGROUND OF THE INVENTION The present invention is an improvement on the method of casting seamless tubing disclosed in US. Pat. No. 3,487,876, granted to me Jan. 6, I970.

In my former patent for casting seamless tubing. molten metal is fed between the walls of an outer revolving cylindrical matrix or mold and an inner revolving cylinder, said mold parts revolving in the same direction at the same speed. The spacing of the walls determine the thickness of the tubing. The metal and tubing were fed by gravity and the mold parts were water cooled to set the molten metal to tubular shape for cutting into desired lengths.

SUMMARY OF THE INVENTION The present application generally functions on the same principle and differs from my prior structure and method mainly in the step of positively feeding the cast tubing to control the speed at which the tubing is withdrawn from the mold and perhaps to some degree the density of'the cast metal. The tubing is always engaged by the feed rolls and no particular weight is imposed on the metal in or leaving the moldso that the finished product is of uniform quality and may be cut off at any length.

The present invention also differs from my former patent in that a gaseous medium such as air is employed as the coolant in the inner stationary portion of the mold instead of water and is injected into the mold at regulated pressures to aid in supporting the wall of the tubing as it is being formed. Water is employed in the cooling of the outer rotating portion of the mold at regulated volume flow. The metallurgical properties such as carbon content may be controlled by injecting suitable compositions or gases into the gaseous coolant.

BRIEF DESCRIPTION OF THE APPLICATION DRAWINGS The invention will become more apparent from a consideration of the accompanying drawings constituting a part hereofin which like reference characters designate like parts and in which:

FIG. I is 'a vertical cross-section partially in elevation of the upper portion of a continuous casting machine embodying the novel features of my invention;

FIG. 2 is a continuation of FIG. 1, comprising a side elevation of the lower portion of the machine of FIG. I, which is the feed and cut-off machine;

FIG. 3 is a end view of the drive roll and motor;

FIG. 4 is a top plan of a plurality of drive rolls angularly spaced to engage the formed tubing;

FIG. Sis a top plan of a drive roll and motor illustrating the gripping action and release of the drive rolls, taken on the line 55, FIG. 4;

FIG. 6 is a cross-section taken along the line 66, FIG. 5, and

FIG. 7 is a wiring diagram showing the electrical connections of the drive motors, thermo-couple and magnetic actuators by which the sequence of operations is maintained and controlled.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1 of the drawings the numeral I designates a housing having flanges 2 and 2a resting on a lateral support 3. An outer mold 4 is mounted on roller bearings 5 to rotate in housing I, and is provided with a relatively thin cylindrical matrix portion 6 of molybdenum or other heat resistant material such as platinum to prevent fusion of the mold surface with the molten metal 7 that is fed from ladle 8 to hopper 9 which is provided with heating coils 9a to maintain a suitable predetermined temperature of the metal.

Housing I is provided with a stationary flange 12 that has the mold portion 4 journalled therein. The mold has a ring gear 14 that meshes with teeth of a pinion 13 at the end of spindle 22. The mold 4 is rotated by a motor 15, FIG. 2, having a shaft 16 journalled in flange 2, FIG. 1. The end of shaft 16 is provided with a pinion gear 20, FIG. 1, that drives gear wheel 21 mounted on spindle 22 journalled at 23 in bracket 24 on housing 1. Mold 4 is journalled at 25 on flange 12.

There are two cooling systems, one for the rotating outer mold part 4 and the other for the stationary inner bell-shaped mold portion 26 which constitutes a pressure chamber. The outer mold 4 has an outer wall 28 open at the top and a partition wall 29 open at the bottom. The coolant such as water 30 is supplied by a pump 31 driven by motor 32, from a sourcethrough pipe line 33 and returned through line 34. The inner mold or hell 26 is cooled by a gaseous medium such as air or gas from pump 37 driven by motor 37a through duct 38 and spray heads 39 and 40. Head 40 is slightly smaller than the inner wall of tubing 55 to provide enough space that will permit an air blast to blow out accumulation of scale, etc., from the bell chamber while permitting the build up of pressure below bell 26 to support the tubing wall against outer mold 4 and maintain its cylindrical shape. Head 40 is also equipped with safety valve 40a to maintain a predetermined pressure.

The pressure of the gaseous coolant may be controlled by regulator 41. Numeral 42 designates a .container for a powderous composition or a gas which may be supplied to line 38 through a regulator 43 to enter the gaseous coolant flow stream to control the metallurgical or physical characteristic of the cast tubing. Duct 38 is provided with a thermostat 44 attached to a refractory tube 44a for controlling the rate of flow of the coolant to maintain a predetermined temperature of the metal in the mold.

With reference to FIG. 2 of the drawings, roller cages 45 and 46 having rollers 47 and 47a mounted on annular tracks 48 and 49 are provided with ring gears 50 and 51 driven by motor 15 through pinions and gear wheels 52 and 53, and 52a and 53a. The roller cages 45 and 46 are revolved at the same speed as outer mold 4 of FIG. I to avoid abrasions of the surface of finished tube 55 by feed rollers 58. Lateral structural members 60 and 60a support tracks 48 and 49. A cut off mechanism generally designated by numeral 61 is mounted on support 60 and is operated at timed intervals to cut-off the length of tubing desired.

The roller cages 45 and 46 are supported against lateral displacement by peripheral bearings 72 and end bearings 73 on flanges 74, FIG. 2. Walls 74a, FIG. 2,

extend to flanges 2 of the mold 4 as shown in FIG. I and to the support 60, FIG. 2.

The feed rolls 58 and their operating mechanism will now be described in connection with FIGS. 3 to 6 of the drawings. As shown in FIG. 4 three sets of feed rolls generally designated by number 58 engage the finished tubing 55 at vertically spaced intervals (FIG. 2), six sets of rolls being shown in each cage. Rolls 58 consist of two parts, a non magnetic squeeze roll 75 and a motor driven roll portion 76. As shown in FIG. 6 roll 76 is driven by motor 77 having shaft 78 connected to a sungear 79 driving orbital gears 80 journalled in roller 76 and 81. The teeth of gears 80 engage the teeth 82 of planetary gear 83 that rotates with roller 76.

Roller 75 is mounted on hub 85 which is journalled on a spindle 86 integral with roller 76, the hub 85 being journalled on spindle 86 at 87 and 88. Non-magnetic roll 75 which is held by a key and keyway 75a to hub 85 and flange 90 is a free-riding roll assembly, and turns when tubing 55 is moved in a downward direction when motor driven roll 76 is turned. Motor 77 which turns roll 76 is stopped when a predetermined length of tubing 55 has been formed, with switch 97, FIG. 7, causing electromagnet 91, which is stationary, to be energized thus pulling and holding flange 90 on hub 85 to force non-magnetic roll 75 toward roll 76 and act as a brake, squeezing and holding the tubing 55 while being severed.

With reference to FIG. 2 the rollers above and below support 60 must be synchronized to operate in the same direction of rotation and at the same speed. Roller cages 45 and 46 are rotated at the same speed as tubing 55 by motor through gears 52 and 53 and 52a and 53a. FIG. 3 shows the circuits 95 of magnets 91 and motor 77 connected with the power line through slip rings 96.

The operation of the above described tube forming machine and feed mechanism is as follows: Motor 15 is energized to rotate the outer mold 4 and feed roll cages 45 and 46 and motors 77 are energized to actuate roller 76 at predetermined speeds.

Pumps 31 and 37 are actuated by motors 32 and 37a, respectively, to supply the liquid and gaseous coolants to the mold 4 and pressure bell 26, respectively, for maintaining a predetermined setting temperature of the metal in the mold.

The feed rolls 58 are operated to withdraw the tubing from the forming machine at a speed to control the density ofthe metal in the cast tube 55. The metallurgical properties of the gaseous coolant may be controlled by regulator 43 which introduces apowderous or gaseous composition to produce desirable physical properties in the finished tubing.

At predetermined intervals, the cut off saw motors 68 and 69 are energized to cut off lengths of tubing when pistons 65 and 66 are actuated by cylinders 63 and 64.

Switch 103, FIG. 7, energizes motor 32 of liquid coolant pump 3], switch 102 operates motor 37a of air pressure pump 37, and switch 104 energizes motor 15 which operates outer mold 4 and roller cages 45 and 46. When thermostat 44 records a predetermined temperature, current passes through relay 37b, switch 99 and switch 32a to motors 77. When a predetermined length of tubing 55 has been formed, the current is turned off at switch 99 thus stopping motors 77. Electromagnets 91 are energized by switch 97 to hold tubing 55 from drifting downward. Switch 98 energizes cut-off saws motors 68 and 69. After severing the tubing and switch 99 is in contact position again, the circuit will be broken using switch 32a. Speed regulator 100 is adjusted to operated the rollers 58 in the lower cage at high speed to rapidly move severed tubing downward until the top of the severed tubing is down through the last feed rollers 58. Regulator I00 is then set to normal speed. Switch 32a is placed in contact position again and all motors 77 are operated at the same speed.

To start the operation, a blank tubing shall be rolled upward through the rolls 58 and set with adjusting screws 58a, FIG. 2, to the bottom of inner bell-shaped mold 26. A suitable sealer such as ganister clay is employed between the blank tubing and bottom of inner bell-shaped mold 26. The liquid coolant is pumped into the outer mold 4. The molten metal from ladle 8 is poured into hopper 9. Pump 37a forces air through duct 38 to build the necessary pressure in inner bellshaped mold 26 to support the metal against the mold wall 4. The outer mold 4 and cages and 46 are rotated by motor 15. Rollers 76 driven by separate motors 77 move cast tubing downward. The weight of the hot metal with the pull of gravity will follow the blank downward. As the metal enters the pressure chamber, the air pressure forces the cast metal against outer mold wall 4 and is set and chilled into a tubular shape.

There is a slight clearance between the inner wall of the tubing and spray head 40 to allow for shrinking and to allow forced air to pass between spray head 40 and the tubing inner wall to blow loose any scaling which might form due to the tubing being cooled. Tubing 55 will continue to be rolled downward to the high speed cutting off tools 68 and 69.

It will be obvious that changes may be made in the details of construction without departing from the principles herein set forth.

I claim:

I. In a machine for casting seamless tubing, comprising:

a. a stationary housing,

b. an outer mold positioned within said housing,

c. means for mounting said mold for rotation relative to said housing,

d. means for cooling said mold,

e. a stationary, open bottom pressure bell mounted within said mold, said bell being dimensioned relative to said mold so as to provide an annulus therebetween approximating the diameter of said tubing,

f. means for feeding molten metal into said mold above said bell,

g. means for delivering a gaseous cooling medium under pressure to the area within and below said bell, said gaseous cooling medium serving to cool the tubing formed in said annulus and pressurized the interior wall of the formed tubing below the annulus surrounding said bell thereby to support said tubing against said mold in such region and prevent collapse of such tubing, and

h. a feed mechanism for controlling the feeding of said tubing from said mold consisting of a plurality of spaced drive rollers having a periphery approximately the shape of the tubing, means for mounting said drive rollers for rotation at the same speed as said mold, means for driving said drive rollers at a predetermined speed, braking rollers associated with said drive rollers for holding said drive rollers and thus said tubing to permit the same to be severed.

2. The machine of claim 1 further including means for cutting off a length of the formed tubing at predetermined intervals. v

3. The machine of claim 1 further including means for adding a composition to the gaseous cooling medium to expose the metal of the tubing to a predetermined metallurgical change in its physical properties.

4. The machine of claim 1 wherein said gaseous medium is air and further including means for adding a second gas to said gaseous cooling medium to expose the metal of the tubing to a predetermined metallurgical change in its physical properties.

5. The machine of claim 1 further including means for regulating the rate of flow of the gaseous coolant to the metal inside the mold to control the density of the metal for a predetermined rate of flow of metal through said mold.

6. A method of casting seamless tubing into a revolving mold having positioned therewithin in spaced relation a stationary, open bottom, pressure bell, compris- 6 ing the steps of:

a. pouring molten metal into the space between said mold and said bell, b. cooling said metal so as to form the metal into a tubular shape, 7 c. supplying a gaseous cooling medium under pressure to the area below said bell for pressurizing the interior wall of said tubing to prevent collapse of the same, and d. controlling the feeding of the tubing from said mold by engaging the periphery of said tubing with a plurality of spaced drive rollers, rotating said drive rollers at the same speed as said mold, and clamping said drive rollers at desired intervals of time to permit said tubing to be severed, and e. severing said tubing while said drive rollers are clamped. 7. The method of claim 6 further including the step of controlling the metallurgical properties of said tubing by the addition of a metal treating medium to said gaseous coolant.

. 8. The method of claim 6 wherein the cooling of said tubing is effected by water cooling the exterior of said mold and cooling the interior of said tubing by said gaseous cooling medium. 

1. In a machine for casting seamless tubing, comprising: a. a stationary housing, b. an outer mold positioned within said housing, c. means for mounting said mold for rotation relative to said housing, d. means for cooling said mold, e. a stationary, open bottom pressure bell mounted within said mold, said bell being dimensioned relative to said mold so as to provide an annulus therebetween approximating the diameter of said tubing, f. means for feeding molten metal into said mold above said bell, g. means for delivering a gaseous cooling medium under pressure to the area within and below said bell, said gaseous cooling medium serving to cool the tubing formed in said annulus and pressurized the interior wall of the formed tubing below the annulus surrounding said bell thereby to support said tubing against said mold in such region and prevent collapse of such tubing, and h. a feed mechanism for controlling the feeding of said tubing from said mold consisting of a plurality of spaced drive rollers having a periphery approximately the shape of the tubing, means for mounting said drive rollers for rotation at the same speed as said mold, means for driving said drive rollers at a predetermined speed, braking rollers associated with said drive rollers for holding said drive rollers and thus said tubing to permit the same to be severed.
 2. The machine of claim 1 further including means for cutting off a length of the formed tubing at predetermined intervals.
 3. The machine of claim 1 further including means for adding a composition to the gaseous cooling medium to expose the metal of the tubing to a predetermined metallurgical change in its physical properties.
 4. The machine of claim 1 wherein said gaseous medium is air and further including means for adding a second gas to said gaseous cooling medium to expose the metal of the tubing to a predetermined metallurgical change in its physical properties.
 5. The machine of claim 1 further including means for regulating the rate of flow of the gaseous coolant to the metal inside the mold to control the density of the metal for a predetermined rate of flow of metal through said mold.
 6. A method of casting seamless tubing into a revolving mold having positioned therewithin in spaced relation a stationary, open bottom, pressure bell, comprising the steps of: a. pouring molten metal into the space between said mold and said bell, b. cooling said metal so as to form the metal into a tubular shape, c. supplying a gaseous cooling medium under pressure to the area below said bell for pressurizing the interior wall of said tubing to prevent collapse of the same, and d. controlling the feeding of the tubing from said mold by engaging the periphery of said tubing with a plurality of spaced drive rollers, rotating said drive rollers at the same speed as said mold, and clamping said drive rollers at desired intervals of time to permit said tubing to be severed, and e. severing said tubing while said drive rollers are clamped.
 7. The method of claim 6 further including the step of controlling the metallurgical properties of said tubing by the addition Of a metal treating medium to said gaseous coolant.
 8. The method of claim 6 wherein the cooling of said tubing is effected by water cooling the exterior of said mold and cooling the interior of said tubing by said gaseous cooling medium. 